Are you sure that the other broadcasters that have 16:9 channels dont pillarbox 4:3 content in their playouts and then resample that to loose the pillarboxing when through the playout?
It would surely make sense to have the same ratio all though the playout system and then sort out how you want to broadcast it later?
Also HD broadcasters have to pillarbox 4:3 content and then strip the pillarboxing when they have a downscaled version, unless they play out their SD channel separately as extra cost?
I think if you use the mark one human eyeball to test out your theory, you'll find that in practice it doesn't work like this - the resampling is benign, and the bitrate (+ encoder) is far more important.
In many (not all) viewing scenarios, your box or TV will resample the 544x576 image up to 720x576 or 1920x1080 anyway, so you're not avoiding resampling, just pushing it into domestic equipment after lossy compression. That's worse, not better.
For any content broadcast on an HD channel (even from an SD source, even from a 4x3 source!) the HD channel is by far the best choice, because it has far fewer coding artefacts than the SD channels. The SD>HD upconversion at the BBC, though not perfect, is better than your domestic equipment will do, and it's done before lossy compression which is a big advantage. This is obvious if you watch an old SD programme on an HD display and flick between BBC One SD and BBC One HD.
Cheers,
David.
Well fair enough that the domestic equipment for DTT would usually do the very same resampling that the BBC have to do for their SD channels on Dsat, but in the right environments you could get hardware to ignore the AFD that says 12P16 and show the 4:3 image as broadcast with the pillarboxing within the 16:9 raster, this would mean the only resampling done would be if you upscaled this on a HDTV, but then like you say you may as well watch the HD version (which I do BTW!)
No, that's why I put "I think" at the start of my sentence.
Also HD broadcasters have to pillarbox 4:3 content and then strip the pillarboxing when they have a downscaled version, unless they play out their SD channel separately as extra cost?
Yes, with HD playout I assume they all use the BBC method = pillarbox + AFD (+ downscale for SD).
you may as well watch the HD version (which I do BTW!)
So given that there's no local 4x3 output, this is a completely pointless discussion?
Alas one of my DVB-T tuners and my DVB-S tuner died, but have been replaced with a SAT>IP tuner which, once a TVHeadend bug is fixed, will have two DVB-S2 tuners per satellite feed (e.g. when recording a low band horizontal channel on one tuner from one cable the other tuner connected to the same cable will be able to record another low band horizontal channel).
That being said my satellite tuners are still last in the priority chain as it's connected via homeplugs and too many HD recordings from them will overload the available bandwidth (I can record all the channels from PSB3 at the same time no problems via USB, but try and record the same channels from satellite and the bandwidth of the homeplugs/network card on my revo runs out
I'm a bit confused about your setup. Why do you need network cables to record channels? Why not have a local HDD on the PC with your tuner cards for recordings?
I think if you use the mark one human eyeball to test out your theory, you'll find that in practice it doesn't work like this - the resampling is benign, and the bitrate (+ encoder) is far more important.
In many (not all) viewing scenarios, your box or TV will resample the 544x576 image up to 720x576 or 1920x1080 anyway, so you're not avoiding resampling, just pushing it into domestic equipment after lossy compression. That's worse, not better.
Correct, unless you're watching on an old CRT your TV and/or box must resample incoming video anyway, unless it happens to match the screen's resolution (which is never for SD channels) and overscan is disabled. Even then the chroma channel has to be upscaled anyway. You're not going to avoid resampling.
As an example, let's take a situation where someone is watching interlaced SD footage on an SD channel (with an HD simulcast) using a Sky box. Even if we ignore all of the resampling done prior to it reaching the playout suite, there's still plenty to be done before it reaches the user's eyes:
- 704x576i/25 image is deinterlaced to 704x576p/50
- 704x576p/50 image is upscaled to 1920x1080p/50 (for HD broadcast)
- 1920x1080p/50 image is downscaled to 704x576p/50
- 704x576p/50 image is interlaced to 704x576i/25 and broadcast
- 704x576i/25 image is deinterlaced to 704x576p/50 by Sky box
- 704x576p/50 image is upscaled to 1920x1080p/50 by Sky box
- 1920x1080p/50 image is interlaced to 1920x1080i/25 by Sky box and sent to TV
- 1920x1080i/25 image is deinterlaced to 1920x1080p/50 and shown by TV
For any content broadcast on an HD channel (even from an SD source, even from a 4x3 source!) the HD channel is by far the best choice, because it has far fewer coding artefacts than the SD channels. The SD>HD upconversion at the BBC, though not perfect, is better than your domestic equipment will do, and it's done before lossy compression which is a big advantage. This is obvious if you watch an old SD programme on an HD display and flick between BBC One SD and BBC One HD.
I wholeheartedly agree that SD content looks better on HD channels due to better compression. However, I don't agree that broadcasters' upscaling is better than home equipment can achieve. On-the-fly upscaling seems to use extremely basic bilinear algorithms on all HD channels, which can be bettered on any half-decent PC for starters. In fact this is a good example that usually bit rate and lack of compression is more important for image quality than the upscaling algorithm used. It's certainly not worth watching DTT versions of BBC SD channels over DSAT versions for.
Upscaling done prior to broadcast though is often excellent, which will be the case for shows that mix HD and SD archive footage.
I'm a bit confused about your setup. Why do you need network cables to record channels? Why not have a local HDD on the PC with your tuner cards for recordings?
A SAT>IP tuner takes the signal from the satellite cable and converts it to IP - this then goes over the network to my media centre where it is treated as an IPTV type stream
SAT>IP - it's kinda awesome - you could have a SAT>IP LNB and connect that to 8 TVs via WiFi for instance!) In my case the satellite feeds are in the lounge so I don't need my dodgy TV "low-loss" coax snaking through the house any more.
I'm a bit confused about your setup. Why do you need network cables to record channels? Why not have a local HDD on the PC with your tuner cards for recordings?
Agreed.
Correct, unless you're watching on an old CRT your TV and/or box must resample incoming video anyway, unless it happens to match the screen's resolution (which is never for SD channels) and overscan is disabled. Even then the chroma channel has to be upscaled anyway. You're not going to avoid resampling.
As an example, let's take a situation where someone is watching interlaced SD footage on an SD channel (with an HD simulcast) using a Sky box. Even if we ignore all of the resampling done prior to it reaching the playout suite, there's still plenty to be done before it reaches the user's eyes:
- 704x576i/25 image is deinterlaced to 704x576p/50
- 704x576p/50 image is upscaled to 1920x1080p/50 (for HD broadcast)
- 1920x1080p/50 image is downscaled to 704x576p/50
- 704x576p/50 image is interlaced to 704x576i/25 and broadcast
- 704x576i/25 image is deinterlaced to 704x576p/50 by Sky box
- 704x576p/50 image is upscaled to 1920x1080p/50 by Sky box
- 1920x1080p/50 image is interlaced to 1920x1080i/25 by Sky box and sent to TV
- 1920x1080i/25 image is deinterlaced to 1920x1080p/50 and shown by TV
I wholeheartedly agree that SD content looks better on HD channels due to better compression. However, I don't agree that broadcasters' upscaling is better than home equipment can achieve. On-the-fly upscaling seems to use extremely basic bilinear algorithms on all HD channels, which can be bettered on any half-decent PC for starters. In fact this is a good example that usually bit rate and lack of compression is more important for image quality than the upscaling algorithm used. It's certainly not worth watching DTT versions of BBC SD channels over DSAT versions for.
Upscaling done prior to broadcast though is often excellent, which will be the case for shows that mix HD and SD archive footage.
So broadcasters dont store SD programs in their playout library as upscaled for HD playout? meaning that each SD program is upscaled frest each time its played out on a HD channel?
Also interlacing and deinterlacing surely doesnt degrade an image like resampling one number of pixels to anothe number of pixels?
Also in the days before SD when the BBC played out 4:3 content on DTT using the centre 540 pixels of the full 720 and so pillerbxing to 16:9 that wasnt ever being resampled in the DTT chain till the viewers box, so if they used a HTPC with both DVB-T and DVB-S tuners the DTT version of BBC channels would have then been better as no resampling work would have been done!
I would say as you cant now get away from resampling of SD content in a HD world (and with HD TVs) that having the least amount of resampling is the best option balancing that with the bitrates of the channel in question.
This in practice means that the HD channel is the best option, as HD TVs will play that natively (with the only resampling done being upscaling at the broadcasters end) and for SD TVs downscaling the HD channel means an SD image thats received with high bitrates so no extra artefacts, thats only been upscaled then downscaled once each.
Using the SD channel for an SDTV will still mean its likely to have been upscaled then downscaled before broadcast then if its a 4:3 program it would have had the pillarboxing cropped off too, then been sent at a bitrate that could be low enough to introduce artefacts, meaning SD channels that have HD simulcasts are worse off than they were before the channel had a HD version and using it for HD TVs is worse still!
A SAT>IP tuner takes the signal from the satellite cable and converts it to IP - this then goes over the network to my media centre where it is treated as an IPTV type stream
SAT>IP - it's kinda awesome - you could have a SAT>IP LNB and connect that to 8 TVs via WiFi for instance!) In my case the satellite feeds are in the lounge so I don't need my dodgy TV "low-loss" coax snaking through the house any more.
I already had the homeplugs to get WiFi downstairs so piggy backing on them works well.
Ah right, never used DVB-IP before. I just run my TV service on the machine that has my tuners inside and any clients can connect over the network to access streams which are essentially just TS files. I run gigabit ethernet to fixed machines and WiFi works fine for my laptop.
So broadcasters dont store SD programs in their playout library as upscaled for HD playout? meaning that each SD program is upscaled frest each time its played out on a HD channel?
Also interlacing and deinterlacing surely doesnt degrade an image like resampling one number of pixels to anothe number of pixels?
The answer to that is the dreaded "depends". If using a good deinterlacer, it doesn't do too much "damage" using it more than once. The Sky box's deinterlacer is pretty crap though. With resampling, if you upscale and then downscale, it could look essentially the same if your scalers are very good. Again, this is definitely not always the case.
But you shouldn't have. As I said they cause serious interference to other users. Bin them and put in CAT 5 cable. That is what it is for. It will solve your bandwidth problems as well. A no brainer.
What and break my neck in the process? Not allowed to run cables and drill holes through the walls round the house - the joys of living in shared accommodation.
The main bandwidth limitation is the ethernet port on my Revo not the homeplugs which can sustain a 100mbps transfer easy enough.
What and break my neck in the process? Not allowed to run cables and drill holes through the walls round the house - the joys of living in shared accommodation.
The main bandwidth limitation is the ethernet port on my Revo not the homeplugs which can sustain a 100mbps transfer easy enough.
More importantly it will save all your neighbours from the RF interference that homeplugs create.
Your posts are starting to look like SPAM. I'm sure there was at least one thread dedicated to this topic. Can't you leave the discussion there?
I would again suggest that lotrjw forgets any theory and even facts he thinks he knows, and just uses his eyes to judge which is the best picture. If you're worried about a little resampling by the broadcasters, I hope you never find out just how much mucking around with the picture the average (or best) TV does!
Comments
Are you sure that the other broadcasters that have 16:9 channels dont pillarbox 4:3 content in their playouts and then resample that to loose the pillarboxing when through the playout?
It would surely make sense to have the same ratio all though the playout system and then sort out how you want to broadcast it later?
Also HD broadcasters have to pillarbox 4:3 content and then strip the pillarboxing when they have a downscaled version, unless they play out their SD channel separately as extra cost?
Well fair enough that the domestic equipment for DTT would usually do the very same resampling that the BBC have to do for their SD channels on Dsat, but in the right environments you could get hardware to ignore the AFD that says 12P16 and show the 4:3 image as broadcast with the pillarboxing within the 16:9 raster, this would mean the only resampling done would be if you upscaled this on a HDTV, but then like you say you may as well watch the HD version (which I do BTW!)
Yes, with HD playout I assume they all use the BBC method = pillarbox + AFD (+ downscale for SD).
So given that there's no local 4x3 output, this is a completely pointless discussion?
Cheers,
David.
Well if you have no HD tuners availible in a HTPC setup then its not pointless.
I'm a bit confused about your setup. Why do you need network cables to record channels? Why not have a local HDD on the PC with your tuner cards for recordings?
Agreed.
Correct, unless you're watching on an old CRT your TV and/or box must resample incoming video anyway, unless it happens to match the screen's resolution (which is never for SD channels) and overscan is disabled. Even then the chroma channel has to be upscaled anyway. You're not going to avoid resampling.
As an example, let's take a situation where someone is watching interlaced SD footage on an SD channel (with an HD simulcast) using a Sky box. Even if we ignore all of the resampling done prior to it reaching the playout suite, there's still plenty to be done before it reaches the user's eyes:
- 704x576i/25 image is deinterlaced to 704x576p/50
- 704x576p/50 image is upscaled to 1920x1080p/50 (for HD broadcast)
- 1920x1080p/50 image is downscaled to 704x576p/50
- 704x576p/50 image is interlaced to 704x576i/25 and broadcast
- 704x576i/25 image is deinterlaced to 704x576p/50 by Sky box
- 704x576p/50 image is upscaled to 1920x1080p/50 by Sky box
- 1920x1080p/50 image is interlaced to 1920x1080i/25 by Sky box and sent to TV
- 1920x1080i/25 image is deinterlaced to 1920x1080p/50 and shown by TV
I wholeheartedly agree that SD content looks better on HD channels due to better compression. However, I don't agree that broadcasters' upscaling is better than home equipment can achieve. On-the-fly upscaling seems to use extremely basic bilinear algorithms on all HD channels, which can be bettered on any half-decent PC for starters. In fact this is a good example that usually bit rate and lack of compression is more important for image quality than the upscaling algorithm used. It's certainly not worth watching DTT versions of BBC SD channels over DSAT versions for.
Upscaling done prior to broadcast though is often excellent, which will be the case for shows that mix HD and SD archive footage.
A SAT>IP tuner takes the signal from the satellite cable and converts it to IP - this then goes over the network to my media centre where it is treated as an IPTV type stream
SAT>IP - it's kinda awesome - you could have a SAT>IP LNB and connect that to 8 TVs via WiFi for instance!) In my case the satellite feeds are in the lounge so I don't need my dodgy TV "low-loss" coax snaking through the house any more.
http://en.wikipedia.org/wiki/Sat-IP
I already had the homeplugs to get WiFi downstairs so piggy backing on them works well.
So broadcasters dont store SD programs in their playout library as upscaled for HD playout? meaning that each SD program is upscaled frest each time its played out on a HD channel?
Also interlacing and deinterlacing surely doesnt degrade an image like resampling one number of pixels to anothe number of pixels?
Also in the days before SD when the BBC played out 4:3 content on DTT using the centre 540 pixels of the full 720 and so pillerbxing to 16:9 that wasnt ever being resampled in the DTT chain till the viewers box, so if they used a HTPC with both DVB-T and DVB-S tuners the DTT version of BBC channels would have then been better as no resampling work would have been done!
I would say as you cant now get away from resampling of SD content in a HD world (and with HD TVs) that having the least amount of resampling is the best option balancing that with the bitrates of the channel in question.
This in practice means that the HD channel is the best option, as HD TVs will play that natively (with the only resampling done being upscaling at the broadcasters end) and for SD TVs downscaling the HD channel means an SD image thats received with high bitrates so no extra artefacts, thats only been upscaled then downscaled once each.
Using the SD channel for an SDTV will still mean its likely to have been upscaled then downscaled before broadcast then if its a 4:3 program it would have had the pillarboxing cropped off too, then been sent at a bitrate that could be low enough to introduce artefacts, meaning SD channels that have HD simulcasts are worse off than they were before the channel had a HD version and using it for HD TVs is worse still!
Usually, yes.
The answer to that is the dreaded "depends". If using a good deinterlacer, it doesn't do too much "damage" using it more than once. The Sky box's deinterlacer is pretty crap though. With resampling, if you upscale and then downscale, it could look essentially the same if your scalers are very good. Again, this is definitely not always the case.
What and break my neck in the process? Not allowed to run cables and drill holes through the walls round the house - the joys of living in shared accommodation.
The main bandwidth limitation is the ethernet port on my Revo not the homeplugs which can sustain a 100mbps transfer easy enough.
I would again suggest that lotrjw forgets any theory and even facts he thinks he knows, and just uses his eyes to judge which is the best picture. If you're worried about a little resampling by the broadcasters, I hope you never find out just how much mucking around with the picture the average (or best) TV does!
Cheers,
David.